Electronic devices, such as mobile phones and smartphones, are generally provided with an electromagnetic shielding layer to prevent a malfunction due to electromagnetic noise that is emitted from electronic components mounted in the electronic devices. It is necessary for printed wiring boards mounted in the electronic devices, in particular, flexible printed wiring boards having flexibility, to ensure durability for mounting the components on the surface of each printed wiring board. Accordingly, the printed wiring board is generally provided with a metal reinforcing plate. Patent Literature 1 discloses a printed wiring board having a configuration in which the printed wiring board is electrically connected with a conductive reinforcing plate through a conductive adhesive layer, to thereby enhance the shielding effect.
Also, a technique is known in which a surface of a metal reinforcing plate is nickel plated to effectively eliminate electromagnetic waves emitted by electronic components, to thereby improve the conductivity. However, there is a problem that it is difficult to bond the metal reinforcing plate to the conductive adhesive layer.
In this regard, Patent Literature 2 discloses a printed wiring board having a configuration in which a ratio of a surface area of nickel hydroxide (Ni(OH)2) to nickel (Ni) on a surface of a nickel plating layer formed on a metal reinforcing plate is in a range from 1.8 to 3.0.